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I suppose there's nothing wrong about the idea that a cognitively separated person could cognitively function as anybody else. But brain as I understand it always needs a potential from some sense. If I suddenly lost all my senses and my brain would stop working for a second would I be able to recover my brain activity?

Otherwise, the brain keeps the same electrical impulses running in the brain so you can't really think of anything new, right? I am really interested just in the way the brain creates new electrical potentials, "just on his own."

$\begingroup$By 'separated person' you seem to mean a person who has lost all of his/her senses? You seem to be interested in what happens when this occurs, and presume (wonder whether?) the brain would 'stop working', implying that there no longer is any neural activity due to the lack of external impulses. This question attracted a lot of close votes. I advise you to attempt to rephrase it in case this is what you mean.$\endgroup$
– Steven Jeuris♦May 16 '16 at 16:57

$\begingroup$Your brain stores a bunch of knowledge (memories) that it uses to construct moment-by-moment experience, so your brain would still be doing stuff without exteroceptive input.$\endgroup$
– mrtMay 17 '16 at 0:53

$\begingroup$@mrt Ok, but where does the electrical impuls arise from in the first place?$\endgroup$
– ProbablyMay 17 '16 at 6:55

2 Answers
2

I am really interested just in the way the brain creates new
electrical potentials, "just on his own."

and

whether [sic] the brain would 'stop working', implying that there no longer is any neural activity due to the lack of external impulses.

If you were to theoretically disconnect the brain from all sensory input, there could be several sources of activity. For example:

Random noise. Neurons are messy objects, there are many small and large molecules floating inside and outside the cells. Furthermore, the membranes themselves are relatively dynamic, and are studded with receptors, ion channels, and other proteins, some of which migrate regularly (see Lipid rafts). The ion channels (e.g. sodium and potassium) that contribute to the electric currents that generate action potentials, can be affected by thermal fluctuations, and thus change their open-closed states in a stochastic manner. Notice the fluxuations in Figure 1 of Horn and Vandenberg (1984) obtained from a single sodium channel.

Some cells fire without any external stimulation. Central pattern generator circuits is one example, and pacemaker neurons is another. Take a look at Figure 1 of Alving (1968) where an isolated neuron exhibits regular spiking without any external input. One can imagine that one such spiking cell could be connected to other neurons and could cause them to spike as well.

Gain control mechanisms might amplify noise. In your scenario, if the brain is not receiving sensory input, the natural gain control mechanisms, attempting to maintain a certain activity range, might increase amplification to such an extent that the thermal noise fluctuations become consciously perceived. For example, sensory deprivation can result in hallucinations, which might be explained by noise amplification by gain control mechanisms. Similar mechanism can also be seen in the Ganzfeld effect

Overall, any one or a combination of the mechanisms described above could cause spontaneous brain activity without external stimulation.

Physics

Perhaps you are asking, "Where would the energy, or the electrical potential, come from?" Short answer: Sugar. Or, at the cellular level, ATP. Point is -- nerve impulses from the senses are [probably] not the brain's main source of energy.

Internal Stimulation

The five senses provide external stimulation to the brain. But that stimulation takes time to spread through the brain. Not only that, the brain's operation is not a one-way street. Signals can (and do) backpropagate. So, cutting off input for a second will not instantly reduce signal transduction to zero. Over time, yes, overall activity would likely decrease significantly. You could test this by putting someone in an isolation tank and doing an MRI. (Sensory input isn't totally muted in this scenario, but it's clearly reduced.)

The human brain certainly has internal mechanisms that allow the mind to recall previously experienced stimuli. Ever heard the phrase "the mind's eye"? That's one name for the thing that allows us to remember things we've seen, heard, touched, or tasted before -- and imagine experiences we've never actually had. Art, creativity, and even hallucination come to mind. (More on that last one in a second. But first...)

...Let's talk about dreams! The separated person's state is a lot like sleep. During sleep, sensory input is chemically muted, or at least turned wayyyyy down. The mind doesn't pay as much attention to its surroundings. If you sleep especially long, the mind 'gets bored' and finds ways to entertain itself, like dreaming. Think about a prisoner that's been locked up for years, whose main source of entertainment is, in fact, the self. This is another example of the idea: When no novelty exists in the stimulation from the outside world, the self works to manufacture the novelty it craves.

Also, drugs. Hallucinogenic chemicals like psilocybin (found in "magic" mushrooms), LSD, and DMT can cause people to ignore their senses in favor of more novel stimulation generated internally. DMT users often use "dreamlike" to describe their experiences, and the parallels between a hallucinogenic "trip" and an ordinary "dream" are pretty obvious.

So, suppose your senses are cut off suddenly. Unless you have never dreamed, visualized something, heard a song in your head, had a sexual fantasy, or otherwise imagined something, I don't think your mind would "stop working"!

Artificial Neural Networks vs. Human Brains

A brain is one kind of mind.

Another kind of mind is an artificial neural network, or ANN. To my knowledge, all ANNs have inputs.

A brain without senses would be like a neural network without inputs. For the reason I just stated, this doesn't really compute (ha.) But, a biological brain has a little more to it than the simple little computer brains that run our search engines and social networks. ANNs only simulate SOME features of human brains -- specifically, neurons and the signals they pass to each other. In addition to the neurons and signals, human brains have lots of chemicals, like sugar and neurotransmitters, that affect their operation.

Most ANNs are designed to take one set of inputs and turn it into one set of outputs. For a human, "one set of inputs" is not clearly defined, because our existence does not appear to be framewise (until MAYBE you get REALLY into physics). We receive input continuously, and produce output continuously. Lots and lots of of operations per second!

The point is: For a simple feed-forward neural network, cutting off input would cause it to stop functioning, yes. But there are versions of neural networks (convolutional, I think?) that feature neurons that feed back into previous layers, and those, like the human mind, will continue producing output long after input is reduced to zero. In fact, it would take a very specific (and you could say improbable) neural network to produce zero output when given zero input. Most of the ones I've seen are initialized with some random weights. I guess a human brain isn't exactly random when it grows. But a baby kicks (output) in the womb, before it's received much "input"!

$\begingroup$"To my knowledge, all ANNs have inputs." - There are ANNs where inputs are deactivated after a time and new patterns arise from random perturbations. Unfortunately, the interesting work by Stephen Thaler is not very well documented and covered by a questionable patent.$\endgroup$
– danijarMay 26 '16 at 14:53